Paper boat, paper canoe, paper coracle...

Paper boat, paper canoe, paper coracle...

I see a few threads here dealing with the topic of the paper canoe. There is a resource on the web that deals with making canoes out of paper:http://kcupery.home.isp-direct.com/index.htmland another (among many) that offers designs for a cardboard boatshttp://www.thecardboardboatbook.com/There's also a major inspirational journey to be read by N. H. Bishop-- Voyage of the Paper Canoe, 1878 http://www.ibiblio.org/eldritch/nhb/paperc/intro.htmlHowever, it needs to be pointed out that 19th century papers were very different from today's commercial papers and while whole industries existed -- making furniture and boats from paper, the paper used contained more that just pulp -- rags were a common ingredient for instance.I've done sculpture and puppetry often with paper clay and I'm now back exploring paper and in many ways I prefer it to clay.

But I'm also back confronting my chronic obsession with the paper canoe. But when I reconsidered my boating needs I decided that maybe a canoe is more trouble than it's worth no matter what it is made from, given what I intend to use it for ( around the inlets and coastal wetlands near where I live boating and fishing.) and its length. So I started exploring coracles then found, to my mind, the quintessential paper (sea going)craft project:Thuyá» n thĂșng coracle.

These are traditional woven from bamboo in Vietnam-- they are a floating bamboo mats in a frame -- and represent several types of small craft that are basket boats -- and still built and used in Vietnam, India and Iran. So I'm building one of these . They are simply woven and painted with resin or pitch to waterproof them. Fisherman paddle them out to sea and ever through the breakers.A 2 metre diameter Thuyá» n thĂșng has a maximum weight capacity of 1500 kg, and can carry up to 5 people!

So, to give it a word: I'm building a very large papier mache bowl in which I intend to mess about in. My notes, researches, experiments and progress is being logged here:http://kickbike.blogspot.com/search/lab … %20CoracleSince I've had a little bit of background using paper I'm going to rely on irrigation tubing (Agi-pipe)and bamboo skewers to give my coracle structural strength. They are my standbys. I think bamboo skewers, so readily available and so cheap , are a modeler's essential.I've used them like nails, to make arms, and legs for puppets. I've wrapped them in bundles to make rods and drum sticks. So deploying them on a boat for structure comes easily .

Waterproofing?

Interesting enough, traditionally the paper canoe relied on Shellac to waterproof the paper but I also guess that (bees)wax could have been used, as it was in ancient Greece for waterproofing. While I'll never try to rely on Linseed Oil, I'm going to experiment with something similar -- Deks Olje -- which is used on wooden boats today. The problem with relying on a surface cover -- such as with expoxy resin -- is that if that fails you're in trouble straightaway and seasonal touch ups are complicated.

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Thanks for such a thoughtful contribution. It is certainly an interesting subject. I don't know whether you have any experiences of coracles? They are basically very unstable structures and need real skill to handle them without capsizing. One of their great benefits is that they can be strapped to the back and carried reasonable distances. So if you want to look like a tortoise . . . !?DavidO

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I'm familiar with the British Isles coracle and as you suggest, it's rocky.I wondered about that and it seems that porting it on your shoulders is a determination of size and shape regardless of other coinsideration.

The Vietnamese Thuyen Thung (picture below)http://www.flickr.com/photos/21586768@N07/3670438800/is more stable and can vary greatly in size. It is also seagoing where the British coracle is now limited to river use. I'm also in Australia by the way -- no coracles here.

These craft sit 'on' the water rather than 'in' it.

One thing nags me however, in regard to papier mache structure. If I construct a round bowl shape and use quality paper as well as criss crossing the layers where are my stress points?

We could imagine that a parallel would be a china bowl which would break if dropped on a concrete surface, but if I am only dealing with stresses from below and gravity and weight I'm wondering what is the best way to reinforce it.

My problem is that any 'foreign' structure I introduce up flush against the bowl would only promotes stress points around which the boat could fold and split.So a basket frame structure like the English coracle (made from willow when the hull is canvas) won't do. Better that I use the same material as the bowl to construct struts -- a support frame.

When you consider it, consider the engineering, paper has its own structural rules which I'm sure should be understood before trying to apply them and as far as I know none of the 19th century paper canoes had internal frames having been shaped over a mould.

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Hey, this is really interesting. As Sue (Catperson) says, we will be delighted if you reach a point of being able to share pictures with us all.Why 'good quality paper'? It sounds as though you mean expensive stuff. I find that alternating layers of kraft (brown packaging) and bond (office type) with PVA produces a very strong laminate, at no cost. Of course it has to be waterproof so in this case you probably won't use SCMC or wallpaper paste at all. I'm sure you'll try some experiments first.Stress points? You mean where it is most likely to collapse? Well, anywhere really but the weakest area would be around the rim where it would have to be very strong to withstand pressure without collapsing inward. I would have thought that an internal frame, such as you would use with birchbark etc. could only be helpful. The Welsh coracles are a good example, where the outer skin is only strong enough to withstand the water pressure. The rest is done by the frame. I haven't looked at the other coracles you mention, but am just about to. You can make strong frame structures with heavy duty card shaped into squared or triangular tubes but this would be very vulnerable to water ingress.DavidO

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Having looked at your pictures (very nice) I would have thought that the third one makes a good model (the boat, that is). With the paper laminate you would simply be providing a strong skin. A problem would be that the internal face must be as waterproof as the outside and the frame would make this difficult. To overcome this, you could lay aluminium foil a a resist over the frame; laminate over it; remove the foil (with a big turkey ready for the over?); pull off the laminate shell and shellac like mad; slip it back on and fix.What do you think?DavidO

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Well I was going to proceed by creating a mould -- a mound of bagged sand sculptured to shape, covered in cling wrap, and laying the pasted paper on top of this. The shape would be an upside down bowl, you see -- very straightforward. This was how I've done masks, either with clay, paperclay and other mixes as a mould and if necessary you just pulled the framing material apart to retrieve the shaped item once it dried

With that approach any frame-ing would have to be added later, you see.

So imagine I then have this very large bowl made out of <i>papier mache.</i> I then upturn it so that the lip faces up, and then begin to lay down "structure" inside the bowl itself, adding several more layers to the rim, and creating a fan effect frame inside the bowl by laying down bamboo skewers, strapped end to end and adhering them to the 'hull' with further layers of paper -- ie just like a paper fan in fact with bamboo ribs. The only alternative I can imagine to this would be to lay down narrow strips of several layers of paper.

I've actually done experiments before with aluminum foil and found it very resistive to glues but I also don't understand your suggested usage.

On the question of the glues -- I've used PVA and find that since it is plastic it can often whell up and coagulate between layers whereas cellulose glues are much easier to 'merge' with the paper being, essentially, the same material -- plant pulp. What I mean is that I really lay on a lot of hand pressure when I'm laying down paper layers and treat the form and its paper as clay.

I used to make masks by creating a paperclay slip and cellulose glue mix soaking felt cloth in this then working the felt over a face (mask) mould so that any fold in the felt merged with the material as though it was all pulp. Once I had the profile just so I'd then coat it with a PVA/water mix -- thus plasticating it and laying down a undercoat. I'd then often use boot polishes on the masks or melted crayon wax. You get some exciting effects.

I'm approaching the coracle from the same angle as I look upon paper or felt as very malleable stuff that can be 'panel beaten' with hands on pressure. Because of its ease of use, I preferred felt for making masks (so long as it hand some natural fibres in it as not all commercial felt has and pure wool felt is far too dear) , especially with the PVA coating and boot polish as they were always lighter and more flexible than papier mache. In fact if you can imagine how wool felt is turned into items-- hats, bags, etc -- you get an idea of the approach. In the same sense of, I guess, using paper pulp in mould and heating it without glues as one guy I know made his masks.

One approach I thought of was in fact to build any frame out of paper pulp rather than strips of paper....as pulp, in my experience (for better or worse nautically) is stiffer and more brittle than layered paper strips. But glued pulp is so fiddly and hard to work with.

As for waterproofing -- as far as I'm concerned -- any saturation is a problem. The paper boat literature errs towards cellulose glues primarily because there is less chance that the layers will lift from one another and offer channels for water seepage. But no glue is going to replace the protection offered by a good coating and as literature suggests, moisture will eventually find it's way through even an unbroken layer of paint or other surface coating. http://kcupery.home.isp-direct.com/PBAr … kslaw.htmlSo that's the key issue -- what you coat with and, I suspect, how often you coat. And most important sand down the hull to baby bottom smoothness.

Since I'm seabound in this I don't want to drown although I'm only planning to muck about in shallow waters -- inlets, tidal marshes, and creeks -- close to shore but maybe within cooee of an occasional bull shark.(And here really big sharks are known to bite surfboards in two!) However, the main thing to note is that these craft sit on the water, not in it so the pressures are spread evenly as a snow shoe distributes the wearer's weight on snow.

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It all sounds very good sense. I've used the mound of sand technique for one or two things, though not as big as a coracle. You have better drying temperatures in Oz than we do in UK. The aluminium foil was only to prevent the laminate sticking to the frame, if you used that method. I take your point about PVA.I reckon the sand method, followed by inserting a frame is really good. I agree, the pulp would not make a good frame. Flexible bamboo would be great.DavidO(David Osborne, sometimes known as the Ozzard of Wiz)p.s. don't make your lifejacket out of pm. lol

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I can not resist offering a few words of advice on paper boats. (http://kcupery.home.isp-direct.com) is my site and I've spent a number of years on paper boat research... but mostly historical. (Paper mache I'm not so good at and confess ignorance of things you folks do).

Anyway, I was recently in a library that has a sample of the paper from the canoe that Nathaniel Bishop used in his "Voyage of the Paper Canoe", (referenced in the first post). It is clearly as it has been described; a very thick single sheet of linen paper (several mm thick) that has been saturated with a resin of some sort. My guess is shellac, although I was not able to do a chemical test on it (yet).

Secondary literature suggests that the Waters & Sons firm used shellac as part of their "proprietary waterproofing process". They never provided details. I'm guessing it was a mixture of applications of shellac and varnishes or oils (think linseed oil).

Literature also suggests that they used shellac as a glue when making rowing shells out of multiple layers of manila paper.

As for modern canoes of paper, I've seen several that were in sad condition rather quickly. One in particular looked elegant when new, but quickly (one week-end with some rain) became "lumpy". The sad person who had made it used carpenters clue for the paper and a latex paint on the outside. Both are bad news with respect to water.

For amusement some folks build canoes using newspapers and wallpaper paste. They often get a lot of attention, (particularly if you use the local newspaper), but they are indeed temporary boats at best, regardless of how you paint them.

The canoe I built has been surprisingly durable, but I resorted to a marine epoxy resin as a coating inside and out. (I used a Weldwood Plastic Resin to build up paper layers, but that is simply water resistant, not waterproof.) This is sort of cheating I suppose, but I was never really striving for an historical reproduction. More details at: http://kcupery.home.isp-direct.com/PBArtic/TandC.html

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Kenneth Cupery , who should know, captures the quandary in a nutshell: layer by layer waterproofing protection versus coating with outer impermeable shell. I think I'll explore layer by layer in my first model and maybe later, if it is a disaster, try the epoxy approach. While it would be a nice idea to utilize both approaches I doubt that the paper will tolerate the mix. However (thinks he) if I used a coating like Deks Olje, maybe I can use that as I layer the paper so that I build up layer by layer papier mache *and* waterproofing agent.http://www.floodaustralia.net/products/deksolje.htm-- just so long as it doesn't resist the glue which is highly likely. But if the original paper canoe manufacturers used shellac and linseed oil the option may indeed be viable.

I hope to start my experiments with Deks Olje next week -- a Xmas distraction.

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Keeping in mind that I know nothing about these things... but I would like to toss a few ideas out there...

"It is clearly as it has been described; a very thick single sheet of linen paper (several mm thick) that has been saturated with a resin of some sort. My guess is shellac..."

Perhaps it is my interpretation, but it almost sounds like the linen paper was formed into paper a thick, single sheet expressly for this project. Could it have been made right from the fibers into a single sheet, rather than laminated or multiple sheets? It seems that a piece of paper like that would be far stronger, and not subject to the stresses of multiple layers that might have flaws in the lamination that would create weak areas.

Are you dedicated to the idea of a PAPER coracle? Fabric would be stronger, even laminated fabric. Imagine a laminate formed from several sheets of (well-laundered) fabric, with shellac used as the adhesive? And the original, being made from linen fibers, was really closer to being a fabric than a paper. Our American 'paper' money is really 100% cotton fiber, there is no actual 'paper' (wood fiber) in it. As with Bishop's paper canoe, I suspect that the term 'paper' had more to do with the process used to make it than the materials used. For instance, linen and cotton fiber, formed into woven sheets is called 'fabric', but linen and cotton fibers just melded together is called 'paper'. Linen and cotton fibers are far, far stronger than the poor grade of paper produced today as kraft paper or anything similar.

Wouldn't using a non-waterproof adhesive be begging for problems? One slight abrasion of the coating, and I would think the moisture would move laterally through the skin.

When boatmakers use fiberglass and resin, they are impregnating the fiber with the resin, not just adding it on the surface.

And I think David is correct in that the rim is your weakest point, as it will tend to flex as the weight (you) in the coracle shifts. And it would seem that the rim would flex more without a frame than with one. I cannot visualize anything stronger for the purpose than bamboo that would still blend with your adhesive/coatings.

I suspect that plastics of any kind would be out of the question, either as adhesives (PVAs) or framing. The disparity between the materials would probably be too great, esp with the adhesives. I doubt that you will find a single adhesive that will stick well to paper (or fabric) as well as to plastic.

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I agree with what Sue says about the attributes of cotton or linen papers -- and a single piece of "paper' too.I had in the past experimented with adding cotton sheets to papier mache projects but it was always disappointing -- esp compared to felting approaches. It was hard to adhere the two materials. As I said I have used felt before -- for masks-- but a felt that was mainly artificial fibre. It was one sheet sculptured into shape and no paper was involved except in the slip such that I forced the paperclay into the felt as a immersion, embedding the two materials, then sealing it.

The British Isles coracle is made from canvas (and before that, animal skins -- like the Inuit kayak). So technically thats' one sheet of cloth. However, it is still one sheet of cloth that required a protective coating.

Native American paperbark canoes -- such as the Canadian Birch Bark Canoe -- were built using pieces of bark held in place by cedar sheathing strips and pre-bent ribs, and the sections of bark were chalked together with a gum made of pine and spruce resin mixed with fat .

I have an academic article on how the Vietnamese coracles are made ( sent to me by the Vietnam Wooden Boat Foundation) and aside from the question of waterproof coating they are no more than tightly woven baskets which suggests to me that paper mache criss-cross is not beyond practicability. The difference being, at least, that bamboo is stronger than paper and the 'layers' are self contained strips.

Obviously a bamboo basket with frame is going to be quite strong but not necessarily more waterproof than other materials with out a protective layer. The tradition of basket boats in Vietnam is rich and various and some very large vessels are made by weaving them.

The largest of these measures 12 m in length and can have a load capacity of 4 tons.

I've also played around with the glas sheets used in Fiberglas and they make for a strong , very supportive layer.I've used them to seal outdoor sculptures as an experiment but since I hate using the resin, I used a cement and waterpoofing slip instead. Ten years later, they're still doing fine outside so that material is also a structural option -- assuming it adheres. I even built a small model canoe out of Fiberglas/Cement over a Styrofoam form, but --surprize! -- it was a bit too heavy.

A further complication in my mind is that I've also experimented a little with Adobe -- mud,water, straw and clay -- which also presents a waterproofing challenge. While I'm not intending to build a mud boat, the logic of the process is holistic and it can be a trap to reduce your thinking to one aspect or one material element.With Adobe the very worse thing you can do is lay down a protective coating as the wall or oven, etc has to breath and the materials mix has its own interrelated existence any coating suppresses.

If you think back over the Vietnamese and British Isles coracles I think their hull has to move a bit for the design to work in the marine environment. This makes me wary of pursuing the seeming advantages of a rigid outer coating made from epoxy. It would function I guess something like an egg's shell and once cracked....

So I'm thinking better to get patchy seapage rather a than a Titanic tear -- so long as the leak can be fixed with a splash of something.

Re: Paper boat, paper canoe, paper coracle...

Re: Paper boat, paper canoe, paper coracle...

This is a very interesting thread. A really ambitious project and one that could throw up all sorts of surpising results. These little boats "coracles" were new to me. Thanks so much for sharing it with us.

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I love my paper mache canoe. while I was building it almost everyone said it wouldn't work. except those who had built boats or knew something about boat building or papermache. I did use the epoxy to waterproof the exterior and interior and it worked well. the sides flex in and out and the epoxy doesn't crack. I was worried about this but I think it has similar qualities as fiberglass and does flex without cracking. I guess it would depend on how much it's flexed. the sides of my canoe can flex in about a 10mm (if picked up wrong) without cracking.

after seeing my canoe a lady told me they had built some paper mache boats on the farm as kids. I think they coated them with some paint or something. they used them for a while and then they started to get waterloged. they leaned them against the back of the barn and the rain had got them soaked through. then the cows eat them.

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Ratbagradio, you say that the Vietnamese coracles are woven, but from what? Many of the old Native American water carriers were tightly woven baskets from plant materials, so may I assume that those coracles are also woven from grasses or reeds? I am thinking that after centuries of making them, they probably prefer to weave them out of plant materials that have some natural water resistance.

"I think their hull has to move a bit for the design to work in the marine environment." Why? What is your thinking here? As far as I know, a flexible hull is not the norm, and not required. The flex is just another stress. You can float a rock in half an eggshell, but you can't float one as well in half of a soft plastic ball. Please elaborate, if you don't mind.

You mention felt... wool felt comes from sheep (obviously!), so why not acquire some raw wool and make your own felt? It would be an interesting experiment to make some felt from clean but unwashed wool (still containing the natural lanolin), and some from washed wool (which would probably accept adhesive and sealant better).

"So I'm thinking better to get patchy seapage rather a than a Titanic tear ..."

With weakened papier mache, is there a difference? Damp paper is not far from tearing, in my experience. Modern paper isn't very strong under most circumstances.

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Eaten by cows? How organic! No I'm not planning to travel very far from shore.

I'd love to see photographs of your canoe, Don.

In Vietnam the basket boats are constructed from various selected species of bamboo. and yes they have been made for centuries as the coracle is thought to have been a coexisting development from the time of the dugout canoe in Asia, Iran and Great Britain.It is indeed a prehistoric craft.Some researchers suggest that it was used by the Celts to colonize the British Isles.

In Vietnam a coracle usually last about 6 years with everyday use as they are a major fishing and transport craft along the coast and up rivers. They are now also a tourist attraction as any image search will confirm.

Personally, I wouldn't proceed with building a paper canoe as the structural aspects are much more challenging than a 'floating bowl', especially in trying to consolidate the backbone of the thing. The beauty of the round coracle -- even compared to the British oval shape (eg; the Ironbridge Coracle is a classic design)or the pear shape used on one Welsh river -- is that it is structurally balanced and the forces from the water are more evenly shared. That doesn't impact on where you put your feet or where you sit, but it makes for a simpler challenge in regard to reinforced structure. I'm also intending to add some buoyancy apparatus as all coracles will sink if they take in water.

While I'm not going to paddle very far at all,merely a few metres from the shoreline handline fishing (as I say, around inlets and shallow marshes) it's still worthwhile getting inspired and I recommend reading N. H. Bishop-- Voyage of the Paper Canoe, 1878 online at:http://www.ibiblio.org/eldritch/nhb/paperc/intro.htmlHe paddled it down the east coat of the United States.

Some folk have journeyed the length of many of British Isles rivers (eg: 8o kilometres was one journey) in their coracles, and one Welshman paddled across the English Channel in his.

In another example , two Welshman intend to paddle across the English Channel in their canoe made from boutique waterproof paper they make from sheep manure. Their first attempt was abandoned after their hull took in water.

"We thought if we can make a pooh canoe and paddle it across the channel for charity ," one of them told the media, so they could do right by Welsh Air Ambulance.

In further example, Dave Friant, a civil engineer, makes canoes from cardboard http://www.thecardboardboatbook.com/and sells the DIY book.He reckons he has solved the waterproofing issue by relying on coatings that are "environmentally friendly".

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* The construction process includes covering and sealing all exposed seams of cardboard to completely seal the boat from water entering inside the cardboard layers. Once the seams are fully protected, the boat is coated with a rubberized waterproof coating material. When the sealing and coating is done properly the cardboard is protected from water damage. * We have boats that are 23 years old and are still being used! * The recommended waterproof coating is an acrylic elastomeric coating used for waterproofing roofs, concrete, and wooden structures. I have had extremely good results with products from Ames Research in Oregon, USA. I have used both their 'Block and Wall' product and their 'Maximum Stretch' product. * There are numerous products available on the market. Look for 'acrylic elastomeric coatings' when researching your options. * These coatings can be colored with coloring made for acrylic paint. Take your coating to a local paint store and have them color your coating with whatever color you desire.

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Cat's suggestion of cloth got me thinking --so I purchased a cotton/linen blend today and have laid some down on my experimental model boat. I boiled the cloth for 15 minutes first. To my surprise it adhered easily to the underlying paper layers.

I will experiment with cloth on cloth and note the cloth mache threads here in this forum.

I'm really working the paper and the cloth into the form as I'm a once upon a time sports masseur and I got into sculpting because I trusted my hands' creativity. So I like to really put a lot of pressure on the material with my thumbs.

This is my first model and once I've coated it with chosen coatings I'll be leaving it to float -- loaded with stuff -- in a water trough long term to see how it performs as to strength, buoyancy, and permeability. I even hope to weigh down the model so it spends some time on the bottom. After salvage I'll check the design's weak points.

With the cloth my challenge is to work out how best to lay it down. In way of technique there are a few options.

1) Treat it like paper and layer it strip by strip, one on top of the other.2) Cover a large surface by cutting slits in the cloth and mitre-ing the folds then firming the folds down, maybe even removing overlays.3) Layer the cloth side by side in strips or patches. so that there is no bumpy overlay.

Technically as Cat suggested I could almost use one sheet of cloth and simply cover the hull with that by slitting and trimming where necessary. However I still need the paper to create the shape and deepen the thickness of the hull.

But it seems to me if the cloth really adheres without any hesitancy I can mix and match paper and cloth layers while noting that the cloth is going to shrink as it dries maybe more than the paper will.

I am then forced to wonder:What happens to paper or cloth if they are forced to cohabit with one another for years? What leaches? Is there a significant acidation? Does shrinkage stabilize? Will both media flex or bend or dent in unison with one another, or will they pull at each other's adhesion?

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"I am then forced to wonder:What happens to paper or cloth if they are forced to cohabit with one another for years? What leaches? Is there a significant acidation? Does shrinkage stabilize? Will both media flex or bend or dent in unison with one another, or will they pull at each other's adhesion?"

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I have been researching this challenge in the hope of deciding on a project plan.

The whole question of waterproofing is not simply limited to papier mache . Wooden boat enthusiasts face the same problem with their preferred material so I was keen to address waterproofing from a wooden boat POV.

Traditional coracles are built using bitumen covered cloth for waterproofing but bitumen paint would be too heavy for paper .

Another factor is cost. Marine waterproofing paints are many times dearer than domestic paints.

So I'm thinking of adopting a very radical and rather lateral 'solution' -- assuming it is a solution. I plan to use housepaint acrylic and an oil soaking ingress agent.

Once I have laid down several paper layers ( number?)for the hull, I paint the external surface with several coats of acrylic house paint and let it dry. I then flip the hull over and paint the inner surface with acrylic paint as well so that both paint jobs meet each other and merge within the paper layers between.

Acrylic is waterproof when dry and in effect presents a latex like layer. By doing inside/outside I create two concentric layers of acrylic. Then while the final inner coating is still wet I use its tackiness to adhere a new paper layer over the whole inside of the hull. (I'm thinking that I would have much less adhesion once the paint dries)

I then start laying down my internal structure of bamboo and coat that with more papier mache and cloth layers to a required thickness. I then paint this covered frame with several coats of acrylic to waterproof them using the top layer as a means to stick on more paper. I do this to isolate and 'waterproof' each frame piece.

I let the paint and paper dry

I then coat the frames and hull with more paper mache several layers thick.

I'm not sure yet whether I can apply this concurrently or not yet (I have yet to complete experiments)-- but I want to use Penetrolhttp://www.floodaustralia.net/products/penetrol.htm as a waterproofing agent. Penetrol is a modern version of linseed oil for waterproofing boats and you layer it into the surface so that it takes up the oil to saturation point. My notion is that if the acrylic layer leaks, I can rely on the Penetrol soaked layers to hold long enough for me to return to shore.

Jackie Hall's excellent article here on Waterproofing Papier Mache(2005)http://www.papiermache.co.uk/articles/w … ier-mache/captures some of the frustrating contradictions that appear to unravel when you try to waterproof items. But it seems to me that if you intend to touch up the surface on a regular basis you are not asking of a coating to persevere unattended for ever.

In her sample the test was confused by the fact that she used a oil based house paint ('Gary Gloss') and a outdoor acrylic paint which was brought in a hobby/craft store('Angela Acrylic') when the research and the technology has gone into acrylic outdoor house paints over the last ten years such that they strongly now out perform oil based paints.(She also suggests that some craft supplies are over hyped)

Similarly below these top coatings there was no form of waterproofing.

This is the complication of boat coatings. While underwater and above water line is one important factor, how long the boat stays in the water immersed is another. And this article on Acrylic Paint for boats by Dave Carnellhttp://www.simplicityboats.com/latexcarnel.html puts choice into context -- and he has been painting boats since 1951.

The complication I need to point out is that you cannot mix Penetrol -- or Linseed oil -- with Acrylics although you can mix/blend Penetrol with oil based paints (but not 2 pack expoxies). So I'm trying to get around that by allowing the acrylic paint medium to consolidate and dry first before working in the oil. How well they will co-exist inside the papier mache remains to be seen.

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I am thinking that the oil will not penetrate the acrylic paint to any great degree, if at all. The very nature of acrylic that allows walls to be washed is going to 'fight' absorbing the oil.

If I were you, I would make a small sample piece about the size of your outspread hand and apply the finishes as you plan to do on your coracle, and see what happens. Better to find out now, rather than later.

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Oh I know that the oil won't penetrate the acrylic -- that's either a plus or minus. And I do indeed have several scale models made each designed with and for different coating materials.

So how the coatings co-exist and whether they actually provide some significant waterproofing is now being tested in my kitchen laboratory.Unfortunately, at the moment here it rains every day and is hot and humid so papier mache -- just like washed laundry clothes -- take so long to dry.

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Update:

I have been experimenting with materials and my seemingly rigorous test5s have really put the kibosh on a strict papier mache regime. The glues act to transmit the moisture and the adhesion collapses. Weighed down on the bottom of a tank, the sunken craft turns to lumpy porridge.

The standard solution of using an outer coating of 2 pack polyurethane is not what I want to do. But I was researching waterproof coatings for outdoor wood and concrete and considered 'acrylic elastomeric coatings' -- which while they will suit the job as an outer coating, may be too heavy for papier mache.( so I am told by the paint company).

But really, my consultant said, a very good acrylic/latex outdoor paint will do the same job at much less cost.In fact boaties here swear by a house paint acrylic -- Dulux Weathershield for their boat exteriors above the waterline.Any below the waterline paint is usually an expensive enamel . But today the preference has run to using 2 pack polyurethane. rather than enamels.

Another key consideration was that i wanted to recoat the craft maybe annually if necessary and enamel -- and polyurethane especially -- doesn't lend itself to that easily. With acrylic you wash, sand back a bit and paint. All with water clean up too.

The additive gives we a longer dry time and easier, smoother spread. But the trick I'm exploring is a bit lateral -- I'm using the acrylic paint as an adhesive so that I'm making the model (for now only models) out of Kraft paper and acrylic house paint layer by layer.

I wear disposable gloves and find that I have to dunk the Kraft paper tears in the paint then scrunch them up and wring the paper so that I get a deeper embed of the acrylic. I then apply it by hand to the shape and smooth it down by massaging the layers together.

The acrylic mix however makes the shape very flexible, and I wanted much more stiffness. With a standard papier mache mix I'd get a stuff result.

------Is it the paper or the paint? What if I experimented with newsprint? Should I consider adding cotton or linen (or canvas?) ragging?------

The blend of paper and acrylic can be torn along a seam (like cotton can be) if I don't manage a good level of thickness. So i have to think this is a multi layer project and I may need reinforcement by embedding other materials beside paper.( eg: bamboo, cotton, linen etc?) So far I haven't worked out how to best mesh ther paper layers for greater strength and stiffness.

The general lesson is this: if this works then you could make any structure out of paper and outdoor acrylic paint so long as you re-coated at intervals while it was outside. But the internal structure would remain dry. as each layer is protected by oits own coating of waterproof paint utilized as a glue.

Re: Paper boat, paper canoe, paper coracle...

You are really going into this with great gusto! I was interested in the products you are experimenting with. I am familiar with Dulux weathershield - I painted the front of my cottage with it about 13 years ago and it is still as good as new. I've not heard of the latex paint additive before though. Is it new?

Maybe one or both of these products will help our floating teacup artist?